Cooling unit



Aug. 20, 1935. w. M. STEWART COOLING UNIT Filed July 51, 1933 2Sheets-Sheetl P l I3 P l IE INVENTOR Mia/Lam M 5751/1/00 ATTORNEY/5%Patented Aug. 20, 1935 UNITED STATES PATENT OFFIICE COOLING UNITWilliam'M. Stewart, San Francisco, Calif.

Application my 31, 1933, Serial No. 683,997

My invention relates to means for controlling and reducingthetemperature of enclosures and is especially concerned with means forutilizing a solid, gas-emanating refrigerant, such as solid tcarbon-dioxide or the like, for controlling the temperature within anenclosure such as a cooling chamber.

.An object of my invention is to provide means for cooling an enclosurewith a substantially exact regulationof temperature.

Another object of my invention is to provide a cooling unit which issufficiently light and compactto be readily portable.

Another object of my invention is to provide a cooling unit which iseconomical of refrigerant.

A further object of my invention is to provide a simple and inexpensivecooling unit primarily designed for use with a solid, gas emanatingrefrigerant.

An additional object of my invention is, in general,to improve coolingunits.

The foregoing and other objects are attained in the embodiment of theinvention shown in the drawings, in which.

Figure 1 is a cross-section on a longitudinal plane of a cooling unitconstructed in accordance with my invention.

Figure 2 is a cross-section the plane of'which is indicated by the' line2-2 of Figure 1.

Figure 3 is a view, partly in section, showing in elevation a coolingunit installation in accordance with my invention.

Figure 4 is aside elevation of the cooling unit shown in Figure 1 withthe addition of an aircirculating fan. 1

Figure 5'is ,abottom view of the structure shown in Figure 4. Thecooling unit f my invention is susceptible of a wide range of variation,not only in matte'rs of construction but also in environmentalconditions. with railway express car cooling, .as indicated in myco-pending application entitled Compartment car, filed July 31, 1933,with Serial No. 682,996. The range-of.v usefulness, however, is so greatthat I have chosen for illustration herein a typical cooling unitsuitable for all-around usage.

This'unit, as illustrated, has proved particularly successful inconnection with cooling produce containers on motor trucks, andcomprises a housing 6 which is generally rectangularand is approximatelysquare in transverse cross-sec tion. The housing is made up' of apluralitrof enclosing walls generally fabricated'of a suitable Onevaluable use is in connection 11 Claims. (01. Git-91.5)

insulating material 1. That is, a top wall Bis comprised of insulatingmaterial I sheathed on both surfaces, for example by an outer,preferably metallic covering 9 and an inner metallic lining ll.comparably, the housing incorporates 5 a bottom wall 12 includinginsulatingmaterial l confined between an inner lining l3 anll an outershell 14. An end wall [6 is similarly fabricated of an outer shell l1and an inner shell l8 lying on opposite sides of the insulating materialI. The opposite end of the housing is sealed by a closure 2i comprisinga door structure including insulating material 22, an outer shell 23 andan inner lining 24. The door 2| is preferably tapered to form a tightseal with its jamb 26 and is preferably mounted on hinges 21 andprovided with a suitable latch 28 to maintain the door in closedposition.

The spacing of the various walls is such as to provide a chamber 28therein for the accommodation of a solid, gas-emanating refrigerant,usually in the form of blocks 29 and 3|. Customarily, solidcarbon-dioxide -is utilized as the refrigerant. This material has theproperty of giving off carbon-dioxide gas at suitable tempratures. Thisgas isconsiderably heavier than -air and naturally tends to drop ifunconfined. I

preferably take advantage of such characteristic in practising myinvention. To this end the standard size blocks of refrigerant 29 and 3iare 30 somewhat smaller than the internal dimensions of the chamber 28,so that gas emanating from the refrigerant tends naturally to flowdownwardly in the direction of the arrows 32 through a passage 33between the blocks 3| and the interior shell 24 of the door 2|.

Preferably forming part of the housing 6, but thermally isolated fromthe chamber 28, is a conduit 34. This conduit is defined by the outershell ll of the wall l2 and by a suitably corrugated plate 36 which iscustomarily of metal and provides a heat exchange surface between thematerial within the conduit 34 and the exterior air. Theplate 36, whileillustrated herein as corrugated, can be'ilat or of any suitableconfiguration in order to comply with the desired heat exchangecharacteristics.

To establish communication between the conduit 34 and the chamber 28 Iprovide an outlet duct 31 which pierces the bottom wall l2 and is ofgenerally rectangular shape and of relatively large cross-sectionalarea. Gas flowing in the path indicated by the arrows 32 continuesthrough the duct,asindicated by the arrows 38, and fiows throughthe'conduit 34 as indicated by the arrows I the cycle.

39. In order to prevent blocking of the duct 38 by shifting of therefrigerant blocks 29 and 3|, I preferably providt suitable guards orspacers 4| on the door 2 I, so that when the door is closed the blocks29 and 3| are precluded from sliding over and blocking the duct 38.

I preferably provide means to control the flow to the duct 38, andtherefore on the plate 36 I provide a threaded boss 42 within which isscrewed a threaded shaft 43 carrying a suitable manipulating handle 44.A valve plate46 is mounted on the shaft 43 and can be tightly pressedagainst the duct 38 or can be removed therefrom in order to regulate thepassage'of gas therethrough. Adjacent the boss 42 I provide a sump 41with a drainpipe 48 and a closure cap 49 for the drainage of moisture.While solid carbon-dioxide itself is moisture-free, nevertheless certainatmospheric moisture enters the chamber 28 whenever the door 2| isopened, and after a period of time such moisture collects within thesump 4'! and is discharged through the pipe 48 upon removal of the cap49.

Gas which travels from the duct 38 into the conduit 34 is in neatabsorbing relationship to external air on the opposite side of the plate36 and absorbs heat from such external air at a relaan inlet duct56.piercing the end wall I6. The

passage 54 is partially formed by a closure 51 customarily fabricated ofsheet metal and fitting on the end of the housing 6. The duct 56 is verymuch of the character of the duct 38 but is located adjacent theuppermost portion of the chamber 28, so that the relatively light,warmed gas can return in a favorable location. Gas which returns throughthe duct 56, as indicated by the arrow 58, is quickly reduced intemperature by thermal proximity to the refrigerant blocks 29 and 3| andquickly recycles in the path of the arrows 32 and 39 as previouslydescribed.

In the mentioned fashion there is provided convection circulation in aclosed cycle, with heat absorption through the conduit 36 and return ofthe warmed gases to the relatively cold chamber 28. The pressureexisting in the circuit is substantially atmospheric and, in order tomaintain such pressure and to provide for the escape of gas which isrelatively high in temperature and which is no longer useful, I providean outlet pipe 59 at substantially the highest thermal point in The pipe59 opens into the upper portion of the duct 54 and, while most of thewarm gas adjacent the duct 56 is sufliciently cooled by the refrigerantblocks 29 and 3| to enter the duct 56 and recycle, certain of the gaswhich is too high in temperature is not sufficiently cooled and flowsout through the discharge pipe 59 which communicates with theatmosphere.

In order that flow through the duct 56 will not be blocked by therefrigerant cubes 29 and 3|, I provide suitable spacers 6| on the endwall I6, so that the duct 56 affords a free passage for the returninggas. In accordance with my invention, however, I desire to vary orrestrict the circulation of the gas in order to adjust the temperaturewithin the conduit 34 so that the desired cooling rate can be obtained.To this end I preferably let I28 discharges.

restrict the entrance of duct 56 by a valve 62 which can be operated ina suitable fashion. Ordinarily, the valve 62 is operated in response tothe temperature of the returning gas within the passage 54. To this endthe plate 82 is mounted on a bimetallic strip 83 or other suitablethermostat which is anchored as at 64 on, the casing 51.

In order to control the temperature at which the thermostat 63 isespecially responsive, I provide a cross-shaft 66 which projects fromthe casing 57 and carries a manual operating handle 68 or other suitableactuating device. Mounted on the shaft 66 is an eccentric 69 adapted toabut the strip 63 and thus govern the position of the plate 62 and thetemperatures at which the plate 62 is especially effective. By suitablymanipulating the handle 68 the maximum rate of flow of the refrigerantcan be governed. The temperature within the space or enclosure cooled bythe cooling unit of my invention is held within very close limits by thethermostat. I have found from extensive practice that a deviceconstructed with approximately the proportions shown, espee cially withthe insulation in the walls 8 and the door 22 somewhat thicker than theinsulation in the walls I6 and I2 adjacent the heat exchange members 34and 51, provides a suitable range of operating temperatures.

While the unit as shown in Figures 1 and 2- is suitable for generalinstallation, when the cooling unit is installed within an insulatedchamber I prefer to provide certain modifications. As illustrated inFigure 3, the cooling unit, generally designated IOI, is disposed withinan insulated chamber 02 having walls I03 formed of an outer shell'I04"and an inner shell I06. Genierally, the

space'betWeen theinner and outer w'allsis filled with any standardheat-insulating material I01. In accordance with my'invention, theo'utlet'pipe I08 'forspent gases from the cooling unit IOI, is

tapped through the inner wall-I06 to discharge "into the insulationmaterial I 01 between the inner'and outer walls I06 and I04,respectively. Such discharged gas is usually still lower in temperaturethan the temperature obtaining within the compartment I02, whilecarbon-dioxide gas itself is a good heat insulation material. The gasdischarged into the,space betweenthe walls I04 and I06 is compelled topass completely around the chamber I02 to discharge from an outlet pipeI 09 into the atmosphere, the direction of circulation being indicatedby the arrows III. A baflle II2 prevents short-circuiting of the gasbetween thepipes I 08 and |09.'

While under most conditions of operation the natural, exteriorcirculation past the heat exchange surface 36 is ample, neverthelessunder certain circumstances I desire to accelerate such air flow andthereby obtain an enhanced rate of heat exchange. To this end Ipreferably mount a fan of any suitable character on the cooling unititself. As illustrated in Figures 4 and 5, a cooling unit I2I isprovided with a heat exchange surface I22 of corrugated contour. Theunit includes a casing I23 to which a suitable ,motor I24 ismechanically attached. The motor I24 is part of a blower having a scrollhousing I26 to which an air inlet I 21 leads and from which an air out-The direction of discharge of the outlet I28 is such as to cause acurrent of air induced to flow through the inlet I2'I to spread out andflow along the corrugated surface I22, thereby providing an acceleratedheat transfer through the surface.

exposed heat-exchanging surface along one side of said chamber, a ductestablishing communication between the lower part of said chamber and.said conduit, a second duct establishing communication between saidconduit and the upper part of said chamber, and thermostatic meansdisposed within one of said ducts responsive-to the temperature of thegas circulating in said conduit for controlling the flow of gastherethrough. r

2. A cooling unit comprising a heat insulated housing having a chambertherein for containing a solid gas-emanating refrigerant, a metallicpartition having an exposed heat absorbing surface arranged in spacedrelation along the bottom of said housing, a plurality of ducts piercingsaid heat insulated housing for establishing communication for aconvection circulation of gas between said housing and said metallicpartition, and thermostatic means responsive to the temperature of thecirculating gas for controlling the rate of heat absorption of saidmetallic partition.

3. A self contained cooling unit for refrigerating purposes comprising ahousing of heat insulating material having a chamber therein for holdinga solid gas-emanating refrigerant, a corrugated metallic wall disposedin spaced relation along the bottom of said housing and forming aconduit having an exposed heat-exchanging surface, a plurality of ductsextending through the heat insulating material forming said housing forestablishing communication for a convection circulation andrecirculation of gas through said chamber and between said housing andsaid corrugated metallic wall, and thermostatic means in said conduitfor controlling the rate of the circulation of said gas.

4. A cooling unit comprising a heat insulated housing having a chambertherein for containing a solid gas-emanating refrigerant, a metallicpartition having an exposed heat absorbing surface arranged in spacedrelation along the bottom of said housing, inlet and outlet ductspiercing said heat insulated housing for establishing communication fora convection circulation of gas between said housing and said metallicpartition, a manually controlled valve in said outlet duct, and athermostatically controlled valve responsive to the temperature of thecirculatinggas in said inlet duct, said valves being operable to controlthe rate of heat absorption of said metallic partition.

5. A cooling unit comprising a housing of heat insulating materialhaving a chamber therein for containing a solid gas-emanatingrefrigerant, a conduit having an exposed heat-exchanging surfacearranged outside of and below said housing, a duct in the bottom of saidchamber establishing communication between said chamber and saidconduit, a door adjacent said duct for the introduction of the solidgas-emanating refrigerant, and means carried by said door for holdingsaid solid gas-emanating refrigerant clear of said duct withoutinterfering with the free flow of gas therethrough.

6. A self contained solid carbon dioxide refrigerating unit comprising ahousing of heat insulating material having a chamber for holding aquantity of solid carbon dioxide, means forming a conduit havingheat-exchanging properties through which the gas emanating from saidsolid carbon dioxide may circulate and recirculate by convection, andthermostatic means within said conduit responsive to the temperature ofthe circulating gas for controlling the recirculation of gastherethrough.

7. A self contained cooling unit for refrigerating purposes comprising ahousing of heat insulating material having a chamber for holding a solidgas-emanating refrigerant, means forming a conduit havingheat-exchanging properties through which the gas emanating from saidsolid refrigerant may circulate by convection, thermostatic means withinsaid conduit for controlling the circulation of gas therethrough, andmeans for regulating the range of said thermostatic means duringoperation whereby the rate of gas emanation from said solid refrigerantmay be determined at any time irrespective of the external temperature.

B. A solidified carbon dioxide refrigerating unit comprising a housingof heat insulating material having a chamber therein for containing aquantity of solid carbon dioxide, a heat conducting wall disposed inspaced relation with said housing and forming an exposed heat-exchangingsurface below said chamber, means establishing communication batlweenthe interior of said chamber and the side of said heat conducting wallfor a closed-cycle convection circulation of the gas emanating from saidsolid carbon dioxide, and thermostatic means responsive to thetemperaturevariations of the circulating gas for controlling the flowthereof and thereby the rate of sublimation of said solid carbon dioxideindependently of the temperature external to' said exposedheat-exchanging surface.

9. A solidified carbon dioxide refrigerating unit comprising a housingof heat insulating material having a chamber therein for containing asolid carbon dioxide, a heat conducting wall disposed in spaced relationwith said housing and forming a conduit for a closed-cycle circulationof carbon dioxide gas having an exposed heat-exchanging surface arrangedbelowsaid chamber, means for establishing communication between saidchamber and said conduit to permit a circulation of gas evolved fromsaid solid carbon dioxide, and a thermostatically controlled valveresponsive to the temperature within said conduit for controlling thecirculation of the gas therethrough, whereby the rate of gas emanationfrom said solid carbon dioxide will be determined by the heat absorbedby the gas from said heat-exchanging surface.

10. A solidified gas refrigerating unit comprising a housing of heatinsulating material having achamber therein for containing a solidgasemanating refrigerant, a conduit having an exposed heat-exchangingsurface arranged outside of and below said housing, a duct establishinga path for gas evolved from said solid refrigerant extending from thelower part of said chamber to said conduit, a second duct establishing apath from said conduit to the upper part of said chamber, said ductscooperating with said chamber and said conduit to provide a closed-cyclecirculation of the gas emanating from-said solid refrigerant, and athermostatically controlled valve. responsive to the temperature of thecirculating gas for controlling the recirculation thereof and therebythe rate of sublimation of said solid refrigerant independently of thetemperature external to said housing.

11. A cooling unit comprising a heat insulated housing having a chambertherein for containing a solid gas-emanating refrigerant, a metallicpartition having an exposed heat absorbing surface arranged in spacedrelation along the bottom of said housing, inl-etand outlet ductspiercing said heat insulated housing for establishing communicationfor aconvection circulation and recirculation of gas between said housing andsaid metallic partition, a manually controlled valve in said outlet duct,forcgntrolling the discharge of gas from said chamber, and athermostatically controlled valve responsive to the temperature of thegas circulating between said housing and said metallic partition, saidmanually controlled valve being operable to control the rate ofcirculation of said gas from said chamber and said thermostaticallycontrolled valve being operable to control the rate of recirculation ofsaid gas, whereby the heat absorption ability of said metallic partitionwill be determined.

WILLIAM M. STEWART.

I DISCLAIM ER 2 011,881.William M. Stewart, San Francisco, Calif.COOLING UNIT. Patent dated August 20, 1935. Disclaimer filed July 22,1939, by the assignee, Controlled Rqfrigerants Company Ltd.

Hereby enters this disclaimer to wit: any interpretation of claim 1 thatwill include a structure wherein the thermostatic means is not locatedin a duct remote from the ex osed heat-exchanging surface and is notcontrolled in its automatic operation so ely by temperature changes ofthe gas circulating through the duct in which the thermostatic means islocated.

[Oficial Gazette August 22, 1989.]

